It is the third time that I __have__visited____（visit） the West Lake.为什么要用完成时呢这是固定句型：It is the first time/the second time/the third time...+ (that)-从句从句中要用现在完成时It is the first time i have been here.It was the first time/the second time/the third time...+ (that)-从句从句中用过去完成时It was the first time i had been here.明白了，谢谢～不谢